There were more medical problems for Baltimore Blast coach Kenny Cooper yesterday, causing him to miss opening day of training camp for the first time in the 12 years he has been the team's head coach.

Cooper, 45, was admitted to a local hospital at noon yesterday for a blood clot in his lower left leg and is receiving blood thinner medication.

He is expected to remain hospitalized for 10 days and return to work in two weeks.

Newly named player/assistant coach Mike Stankovic will coach the Blast until Cooper returns to practice.

Cooper was advised by Blast doctors to enter the hospital after he felt continuing discomfort in his leg yesterday morning.

According to Blast vice president of soccer operations Drew Forrester, the leg started bothering Cooper last week when he was in England on vacation. Cooper returned to Baltimore Monday night and was expecting to greet his new-look Blast in practice yesterday.

Blast midfielder Mark Mettrick, who was also in England last week, said yesterday he saw Cooper "two days ago and he was limping."

It is the fourth time in less than three years that Cooper has been ill, and the third time he has been hospitalized.

In January 1989, Cooper developed chest pains shortly before a game at the Baltimore Arena and was forced to go home before the game started. He recovered quickly and missed only one game.

In March 1990, Cooper lost his voice in Dallas and was eventually hospitalized at Greater Baltimore Medical Center for an inflamed esophagus. He missed a home game against the St. Louis Storm.

In April 1991, Cooper felt severe pain in his stomach and was hospitalized for three days. That was diagnosed as an inflamed colon and resulted in Cooper missing the Blast-Maryland Bays game April 28 at UMBC.

Early last night, Forrester said he talked to Cooper in the hospital and briefed him on the first day of training camp that was conducted by Stankovic.

"I gave him the rundown on the team, and he said he was disappointed he couldn't be there to work with all the new players on opening day," said Forrester. "He told me he hoped to be back to practice next week. But he said his health has to come first."

Cooper said last month he was starting training camp earlier than any team in the Major Soccer League "because we have a lot of work to do."

Only six players from last season's team are under contract for the 1991-92 Blast season -- Domenic Mobilio, Billy Ronson, Rusty Troy, Stankovic, Mettrick and Angelo Panzetta.

So there were a lot of new faces, including No. 1 goalkeeper Cris Vaccaro, among the 28 players who reported for the first day of workouts yesterday at William Myers Pavilion in Brooklyn.

Gone are Tim Wittman, Scott Manning, Bruce Savage and Dale Mitchell.

Troy, one of the old faces, said: "We could have a Tim Wittman [among new players] come in here and score 50 goals. The first four or five games the fans won't understand what Kenny [Cooper] did in the off-season. But after that, they will like what they see."

NOTES: Mettrick (recurring groin injury) missed practice yesterday and underwent a Magnetic Resonance Imaging test last night. . . . M Joe Koziol, a former Loyola College standout who was signed as a free agent from the Cleveland Crunch this summer, missed practice. He underwent a bone scan as part of his pre-training camp physical. . . . Stankovic said he doesn't consider Cooper's absence a setback for the team. "I've been around Kenny long enough to know what he wants us to do in practice," he said. "Also, I talked to him Monday night about the prospect of taking over the team in case he had to go to the hospital. I know what I have to do to get us ready for the season."